The present application is directed to a method of using hydroxyapatite or similar materials that promote tissue growth in tissue repair procedures.
Hydroxyapatite (HA) has been around for many years and is the most dependable source for enhancing the “activity” of bone. Hydroxyapatite is used for coating total joint/joint replacements to enhance bone growth into metal prosthetics (“bony ingrowth” prosthetics). In other words, the use of bony ingrowth prosthetics is very popular in the world of orthopedic surgery because the surgeon then does not have to cement or “glue” the pieces in. Porous metals for orthopedic applications have a mesh that allows bone to grow into the metal components. By coating the metal with hydroxyapatite, bone growth into the metal is encouraged. Hydroxyapatite makes such growth faster and more reliable. Hydroxyapatite is also used as a bone graft substitute—to enhance fracture healing, especially in hard to heal fractures such as tibia fractures.
It is known that nano-hydroxyapatite (nano-HA) is also affective for such applications. For purposes of the present invention, nano-HA is defined as HA particles less than 100 nanometers in size, both spherical and nonspherical. When HA is applied to metal components it is done via a high-temperature process sometimes called plasma spraying. This high-temperature process is not suitable for soft tissues because it will destroy the protein materials.
HA can be applied by dipping, but it needs to be partially or fully melted, so it will not be removed by water due to its solubility. HA can be placed on the surface of a soft tissue, hard tissue, metal, ceramic, polymer, but it will quickly be washed off the surface by water. The HA can be partially or fully melted on a substrate by thermally heating (oven or furnace), laser heating, electron beam, or other direct heat source, This direct applied heat will melt (consolidate) the HA and destroy the soft tissue substrates.
Healing of the body, other than healing of bone, occurs with growth of scar tissue/fibrous tissue. Any kind of tendon repair, ligament reconstruction, vascular implant, etc. will heal with scar tissue. Fibrous tissue/scar tissue is usually not as strong as the native tissue, and therefore re-injury is a risk. That is, unlike a bone fracture that will typically appear completely normal after it heals, soft tissue that heals will always look abnormal. If a bone fracture does not unite (“non-union”), it will heal with what is called a “fibrous union”—literally the fracture will bridge with scar tissue. The problem is that the fracture remains unstable and painful and the fibrous union must typically be removed to enable bony union healing.
Another downside of healing with fibrous tissue is that it can stretch out as it heals. Bone does not do this. If healing time can be reduced from, for example, six months to six weeks, such stretching can be minimized such that long-term failure is far less likely. Patients may return much more quickly to work, sports, and other normal daily activity.
Known patent documents in the general field include the following:
U.S. Pat. No. 7,776,600 (Kumta et al.) (U.S. Publication No. 20089/0095820) is directed to a method for production of nanocrystalline HA for use in prosthetic tooth engineering and repair. As discussed at paragraph 0081 and 0082, this HA is used for cartilage tissue engineering and ligament repair by direct injection.
U.S. Pat. No. 6,875,461 (Tanaka et al.) is directed to a method for coating a calcium phosphate compound on a bio tissue substrate where the method causes no damage, using a soaking method. This invention is used in the repairing soft tissue to bone.
U.S. Pat. No. 4,595,713 (St. John) is directed to a medical implant for regeneration of soft and hard connective tissue. Chopped carbon fiber is used in a mass of a copolymer that is molded to the void to be filled or in the shape of the tissue desired and implanted in the patient. The mass is gradually replaced by regenerated tissue.
U.S. Patent App. Publication No. 2010/0178312 (Webster et al.) is directed to compositions and methods for enhancing attachment of soft tissues to metal prosthetic devices. The metal has a nano-textured surface.
U.S. Patent App. Publication No. 2010/0136117 (De Groot) is directed to an HA tissue filler composition suitable for use in soft tissue repair which includes ceramic particles less than 15 or 20 μm. The composition may be in a form that is injectable. Use for reducing recovery time is not discussed.
U.S. Patent App. Publication No. 2010/040668 (Riman et al.) is directed to methods for preparing composite materials which include nanoscale HA. One of the goals is for HA synthesis to take place at room temperature and optional neutral pH to allow the exploration of synthesis with live cells, including those in living organisms. This publication does not explicitly teach use on soft tissue, such as tendons and ligaments.
U.S. Patent App. Publication No. 2010/0047309 (Lu et al.) discloses methods and apparatus for tissue engineering in the form of graft collars and scaffolds. The graft collars comprise a mesh for fixing tendon to bone. Examples are given of ACL grafts.
U.S. Patent App. Publication No. 2009/0317446 (Tan) discloses calcium phosphate nanofiber matrices used to culture bone and dental cells and as implants to treat bone, dental or periodontal diseases and defects.
U.S. Patent App. Publication No. 2007/0071790 (Ameer et al.) is directed to a nano-composite used in soft tissue engineering, such as cartilage, ligaments and tendons.
U.S. Patent App. Publication No. 2007/0258427 (Storey et al.) discloses nano-particle deposition on selected substrates to enhance tissue attachment.
International Publication No. WO/062561 (PCT/US2009/062077) (University of Arkansas) is directed to methods, compositions, etc. in which a material such as HA is combined with a nano-particle composition to form a material delivered to a cell or tissue (including soft tissues). The material may be a coating for an implant.
International Publication No. WO 2008/028194 (PCT/US2007/077560) (Cornell Research Foundation, Inc.) is directed to calcium phosphate nano-fiber matrices used to culture bone and dental cells and as implants to treat bone, repair of body parts, skin grafts, etc.
International Publication No. WO 2008/089109 (PCT/US2008/050940) (Rutgers University) discloses methods for preparing composite materials which include nanoscale HA. At page 5, it is noted that, in the past, HA reaction conditions used high temperatures, high pressures, and extreme pH values such that biological applications are limited.
International Publication No. WO 2008/100534 (PCT/US2008/0018889) (Columbia University) is directed to a nanofiber scaffold for soft tissue and soft tissue-to-bone repair. HA may be incorporated into the scaffold.
International Publication No. WO 2008/070186 (PCT/US2007/025127) (Columbia University) is directed to a scaffold for promoting tendon-to-bone fixation. (similar to Lu application above).
All references cited herein are incorporated herein by reference in their entireties.